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Speaking of slide rules, does anyone know how a wood one fares over time on a 
small boat? I never wanted to trust my beloved K&E on any trip, so I used to 
carry a 6" circular aluminum one.

Hewitt

Sent from my iPad

On Dec 15, 2012, at 8:09 PM, "Greg Rudzinski"  wrote:

> For those that are game for trying the time sight reduction by slide rule 
there are a few ways to gain some accuracy. A means to magnify the slide rule 
scale goes without saying. 
> 
> 1. Use a four place SinHo look-up from the Bowditch trig table.
> 2. Use the Bowditch trig table for the final ArcCos look-up to get LHA (t) meridian angle.
> 3. Slide rule alignment on the two multiplications can be improved if a whole latitude is used.
> 
> This will result in two table look-ups, two slide rule multiplication moves, 
one slide rule division move, and one conventional sum.
> 
> Greg Rudzinski
> 
> 
> 
> [NavList] Re: Longitude by Time Sight Using a Slide Rule
> From: Greg Rudzinski
> Date: 14 Dec 2012 10:18
> 
> K&E slide rule accuracy seems very good for LHA(t) meridian angles greater 
than 50*. There is no need for small meridian angle calculations when the 
ex-meridian method would be used. See attachment for this mornings time sight 
by slide rule. The plot exactly matched an azimuth and intercept by computer 
reduction.
> 
> Greg Rudzinski
> 
> [NavList] Longitude by Time Sight Using a Slide Rule
> From: Greg Rudzinski
> Date: 14 Dec 2012 09:03
> 
> The K&E 10" has been dusted off to perform some time sights using the formula:
> 
> LHA(t)=ArcCos[ (SinHo ~ SindSinL) / (CosdCosL)
> 
> ~ add if contrary name
> ~ subtract if same name
> t = meridian angle
> Ho = true altitude 
> d = declination
> L = Latitude
> 
> This seems to be accurate enough. If Paul Hirose is watching then maybe he 
can do a slide rule accuracy analysis for the time sight using the 10".
> 
> Greg Rudzinski
> 
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